The present disclosure relates to a rotation detection device that is disposed on a panel in an automobile interior or the like.
Typically, a rotation detection device disposed in an automobile interior or the like includes a rotatable operation member that can be moved, for example rotated while being held with fingers, and a detection device that outputs a detection signal corresponding to the direction and the amount of that relative movement. Although a rotary encoder can be used as the detection device, such a rotary encoder is generally expensive, and, thus, the possibility of detecting the rotation using other devices such as inexpensive switches is being investigated.
Conventionally, a rotation detection device using a switch as shown in FIG. 14 is known (see, e.g., Japanese Patent No. 4066037). This device includes a rotatable operation member 80 that is rotated and a rotation detection switch 84 that is for detecting the rotation.
The rotatable operation member 80 is configured to be rotated while being held with fingers for example and a plurality of driving protrusions 82 that protrude outward in the radial directions from an outer circumferential face of the rotatable knob 81. The driving protrusions 82 are arranged on the outer circumferential face of the rotatable knob 81 at constant intervals in the circumferential direction of the outer circumferential face, and rotate unitarily with the rotatable knob 81.
The rotation detection switch 84 is provided with a switch body 86 and a detector 88 that is attached to the switch body 86 such that the detector 88 can move upward and downward (swing) to the left and right. The driving protrusions 82 are sequentially brought into contact with the detector 88 as the rotatable knob 81 is being rotated, and, at each contact, an operation is repeated in which the detector 88 moves downward from an origin position (upright position) in a direction corresponding to the rotational direction of the rotatable knob 81 (a circumferential direction of rotation of the rotatable knob 81) and then returns to the original origin position. That is to say, the rotation detection switch 84 is disposed in an orientation in which the upward and downward directions of the movement (the directions of swing) of the detector 88 match the circumferential directions of rotation of the rotatable knob 81 and the driving protrusions 82. The switch body 86 generates a detection signal each time the detector 88 moves downward and returns.
Well known switches can be used as the rotation detection switch 84, and Japanese Patent No. 4066037 describes an example of a switch 84 of a two-direction three-contact type as shown in FIG. 15. The switch body 86 of the rotation detection switch 84 shown in FIG. 15 is provided with a casing 90 that has a bottom wall 90a, a switch spring 92 that is accommodated in the casing 90, a central contact point 94C and left and right contact points 94A and 94B that are arranged on the bottom wall 90a, terminals 95A, 95B, and 95C that respectively correspond to the contact points 94A, 94B, and 94C, a support shaft 96 that is disposed in the upper portion of the casing 90 and forms a swing shaft of the detector 88, and a pair of left and right cam sections 98A and 98B that rotate unitarily with the support shaft 96. This switch is merely exemplary of the type of switches that can be used.
The switch spring 92 can be made of a metal plate capable of being elastically deflected, and both end portions thereof respectively form spring contact points 92a and 92b that are pressed against the bottom wall 90a. The shape of the switch spring 92 is generally set so as to achieve the following operability. That is to say, the switch spring 92 is set so as to be in uniform contact with the cam sections 98A and 98B from below, so that the detector 88 is held at the origin position as shown in the drawing, and, in this state, the spring contact point 92a is positioned between the contact points 95A and 95C, and the spring contact point 92b is positioned between the contact points 95B and 95C.
In this device, if the rotatable knob 81 is for example rotated in a direction indicated by the arrow 89A in FIGS. 14 and 15, the driving protrusions 82 that rotate unitarily with the rotatable knob 81 are sequentially brought into contact with the detector 88 of the rotation detection switch 84 and move the detector 88 downward in a direction corresponding to the rotational direction (right direction in FIG. 15) (see the dashed double dotted line 88A in FIG. 15). Accordingly, the cam section 98A linked to the support shaft 96 of the detector 88 is lowered, elastically deflecting the switch spring 92 in the direction indicated by the arrow 93A in FIG. 15, and, thus, the two spring contact points 92a and 92b of the switch spring 92 are caused to slide along the bottom wall 90a and are brought into contact with the contact points 94A and 94C. In this manner, conduction is established between the terminal 95A corresponding to the contact point 94A and the terminal 95C corresponding to the contact point 94C via the switch spring 92, and a detection signal indicating that the rotatable knob 81 has been rotated in the direction indicated by the arrow 89A is generated. Subsequently, when the driving protrusion 82 moves past the detector 88, the detector 88 returns to the original origin position due to the elastic return force of the switch spring 92, and the two spring contact points 92a and 92b of the switch spring 92 are moved away from the contact points 94A and 94C.
On the other hand, if the rotatable knob 81 is rotated in a direction indicated by the arrow 89B in FIG. 14, the detector 88 is moved downward in the direction opposite the previous direction, that is, to the left in FIG. 15. Accordingly, the cam section 98B is lowered, elastically deflecting the switch spring 92 in the direction indicated by the arrow 93B in FIG. 15, and, thus, the spring contact points 92a and 92b are this time brought into contact with the contact points 94C and 94B respectively, and conduction is established between the terminals 95C and 95B. Accordingly, a detection signal different from the above-described detection signal is generated.
That is to say, in this device, if the rotatable operation member 80 is rotated, detection signals that vary depending on the rotational direction are intermittently generated, and the rotational direction and the rotational amount are recognized based on the type and the number of the detection signals generated.
In rotation detection devices of this sort, it is an important issue to reduce a rotation detection pitch for the rotatable operation member, that is, an arrangement pitch Pt of the driving protrusions 82 for driving the rotation detection switch 84 in the device shown in FIG. 15 (interval between the driving protrusions 82 shown in FIG. 15). A reduction in the rotation detection pitch, that is, the arrangement pitch Pt enables greater precision in detecting the rotational amount with the rotation detection switch 84 without increasing the size of the entire rotatable operation member including the driving protrusions 82. Furthermore, in the case where a click mechanism that generates a click feel in accordance with the rotation detection pitch is provided, it is possible to improve a sense of operation given to the user by reducing the click feel generation pitch.
However, in this device, there is a strict limitation as to the ability to reduce the pitch Pt of the driving protrusions 82 corresponding to the rotation detection pitch, which is based on providing sufficient distance so as to allow a proper swing movement of the detector 88. If the arrangement pitch Pt is too small, then, after one of the driving protrusions 82 is brought into contact with the detector 88 and moves it downward and then releases the detector 88, the next driving protrusion 82 is brought into contact with the detector 88 before the detector 88 returns to the proper origin position (position indicated by the solid line in FIG. 15). Accordingly, a proper return movement of the detector 88 is inhibited, which causes erroneous detection. In other words, in order to ensure a proper downward movement and return movement of the detector 88, the interval between the driving protrusions 82 that are adjacent to each other, that is, the arrangement pitch Pt has to be set larger to some extent than the swing stroke of the detector 88 (the maximum movement distance of the detector 88 in directions orthogonal both to the direction of the support shaft 96, which is a shaft about which the detector 88 swings, and to the radial direction of swing). Accordingly, a strict limitation is imposed on the reduction in the arrangement pitch Pt.